Process of electrolytically treating tannic infusions of plants.



H. DAMKUHLE'R & H. SGHWINDT. PROCESS OF ELEQTROLYTIGALLY TREATING TANNIGINFUSIONS V APPLIOA'HON FILED mm: 10, me. 975,835.

or PLANTS.

' Patented Nov. 15, 1910.

I a a:

a ti

WWW 575%??? erases.

. posited by the said process,

ran sTATEs PATENT enrich.

LIKERMANN DAMKUHLER AND HUGO SQHWINDT, 0B, IBREMEN, GERMANY.

raocass or Etacraonvrioatm TREATING TANNEC INFUSIONS or PLANTS.

Specification of Letters Patent.

To all whom it may concern: 7

Be it known that we, HERMANN DAM- KoHLnn, apothecary, and HUGO Scnwmnr,apothecary, citizens of the German Empire, residing 'at Bremen, Germany,have invented new and useful Improvements in a Process of ElectricallyTreating Tannic Infusions'of Plants, of which the following is aspecificalllOIla Our invention relates to improvements in a process ofelectrically treatin tannic infusions of plants, particularly of thebark of the mangrove, which are used in themanufacture of leather. Theseinfusions, for ex ample those which are obtained from the bar of themangrove which are particularly rich in tannic acid, often contain red-I brown dye stuffs which in the tanning process impart anon uniformcolorto the leather which impairs its quality; Efforts have heretoforebeen made toremove these dye stuffs from the said infusions bysubjecting the same to the electrolysis; However, these efforts haveproved unsatisfactory, because. either the dye stuffs were notsufiiciently deor a considerable amount. of thetannic .acid wassimultaneously. removed, so that the value of the tannic infusions wasdecreased. The object of our improvements is to provide a process,whereby the saiddye stuffs can be removed from-the infusions n adegreewhich is sufficient for practical pur oses, without, however, impairingthe qua ity of the infusions.

said-infusions metallic'salts are. added the metals of which are thesame as those of the electrodes. v

When treating the infusion within such a cell, the electrolytic hydrogenwhich is liberated is in statu nascendz' and seems to have a reducingaction on the dye stufi's cont-ained'within the infusion, so that thesaid dye stuffs are deposited." The fact that the hydrogen is animportant factor in the process may be recognized from the fact, that atthe end of the process hydrogen is set free.

In the preferred mode of carrying the process into effect bothelectrodes are made .of aluminum and zinc, the anode-is separated fromthe cathode by a porous partition wall, and the electrolyte surrounding"the anode as well. as the'solution added to the tannic infusionsurrounding the cathode both consist of a solution I of a sulfate ofaluminum and of a sulfate of zinc.

For the purpose of explaining the invention, an example of an apparatusadapted for carrying the same into effect has been illustrated in theaccompanying drawing, the figure showing a vertical cross-section of theapparatus.

Within a receptacle a of zinc designed to receive'the tannic infusion tobe treated an aluminum cylinder 0 having perforations b is located whichis preferably supported on insulating feet (I, and which at its top iselectrically connected with the receptacle a of zinc. Within thealuminum cylinder 0 a cylinder 6 of clay is supported on the bottom ofthe cylinder (1 within which a strip f of .zinc and a strip g ofaluminum are located one beside the other. which at their upper ends areelectrically connected with each other. The receptacle a of zinc and thecylinder o of aluminum form the cathode ,,while ,the strip f of zinc andthe strip 9 of aluminum form the anode.

Into the receptacle a of zinc the tannicin added which correspondsto theintensity of the dye stuff, which solution assists in the formation of adeposit. Thecell e of day is filled with soft water having a smallamount of aluminum and zinc sulfate dissolved therein, so that bothelectrodes (1, 0 and f, g

are in solutions of the salts containing their own metals. g I

When treating an infusion of the dark colored bark of the mangrove, thefollowing amounts by weight of the ingredients have proved satisfactory:For 1 kilogram,ofthe dry tannin a solution of about 10 grams of thesulfate of aluminum and of 0.3 gram of the sulfate of zinc in waterisused. For filling the cylinder 6 of clay a solution of grams of aluminumsulfate and 0.3 gram 0 Zll'lC sulfate in 1000 grams of water issufficient. In the electrolysis of the tannic infusion within the cellthe acids of both salts added thereto and of other salts containedtherein pass-into the cylinder 6 of clay, while the tannic acid does notpass Patented Nov.15, i910.

through the same. At the cathode a, 0 the deposits are formed whichcontain a part of the dye stuffs which are injurious in the manufactureof leather, while another part I i of the said dye stufi's remainswithin the infusion and is lightened by reduction.

" If in the course of carrying out the process filtered'samples takenfrom the solution do not show a further lightening, and if in theSolution only minute amounts of sulfuric acid are found, theelectrolysis is stopped, the tannic infusion is .cleared in the'usualmanner and vaporized to the desiredcon -s1stency,

The deposit precipitated from the sion and containing the dye stuffsdoes not contain any material amount of tannin, as

is proved by the fact, that a solution of the same has no tanning actionat all.

In carrying out the process, we have found, that a part of thenon-tannic substances contained iii-the infusion is transformed intotanninff The'metalused as'electrodes in our improved process depends onthe metallic comconsists in, subjecting ,the said infusions" totheelectrolysis withln a cell, in which the tannic infusion forms a bathfhr the cathode which is separated from the anode .by a

I porous partition wall, and in which the 40 bathsfor the electrodescontain'solutions of metal salts the metals of whichare those ,5

Of the electrodes. I

T hrein r bed process of treat-e ing tannic infusions of plants, forexample.

a grove, which consists in subjecting the said 7 those obtained from thebark of the man emcee.

infusions to the electrolysis Within a cell I the anode and cathode ofwhich both consist of aluminum and zinc, and the elec-- trolytes containa solutionof a sulfate of so aluminum and sulfate of zinc;

3. The process of treating extracts con-. taining tannin, which consistsin subjecting them to electrolysis in the presence of dissolved salts ofthe metals of which the electrodes are composed. V

' 4. The process of treating extracts containing tannin, which consistsin subjecting 'them to electrolysis with electrodes each of whichconsists of aplurality of metals and in the presence of dissolved saltsbf the Y metals of which the electrodes are composed.

5. The process-of treating extracts containing tannin, :Which'consistsin separating such extracts by aLporouswall and subjecting them toelectrolysis in the presence of dissolved salts of the metalscomposing-the,

I electrodes.

6. The process for treatingextracts containing tannin, which consists.in separating '70 such extracts; by a porous wall from a-solution ofaluminum sulfate and zinc sulfate, adding a mixture of the samesolutions to the extracts and subjecting them to electrolysiswithelectrodes each of which is composed of aluminum and zinc. v 7; Anelectrolytic apparatus comprising a zinc container, an aluminum memberconnected therewith electrically} and forming the 'cathodewith saidcontainer, a porous cell, and an anode composedaof zinc andaluminum andarranged ;-to 1p into such j porous cell. 7 v r In testimonywhereofwehereunto afiix our signatures in the presence of two witnesses.

j HERMANN nAMKorniEn. r HUGO SGHWINDT. Witnesses:

ERNST Dnnwrrz, FERDINAND Enron.

